JPS6259436A - Communicating method for data - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data communication method that applies particularly, but not exclusively, to mobile data communication systems.

Problems that arise in data communications include, for example, interference due to channel noise, which can cause part or all of the message data to be lost. 2 used for mobile data communication systems
The various transmission protocols were introduced at the IBEE Vehicle Technology Conference (IBEE Vehicular Technology Conference) held in Sanjev, USA in May 1985.
cular Technology Confe-re
P, J, ? on pages 370-374 of the newsletter of nce). The paper “Predicting the Range and Throughput of Mobile Data Recording Systems” reported by Mr. Pei
ge and throughput of mobile
e data systems)”,
). Before explaining these, reference is made to FIG. 1 of the drawings.

FIG. 1 shows a typical data format. The format starts with a preamble PR of 16 inverted bits (1010...10) to achieve bit synchronization in the data demodulator, followed by a 16-bit synchronization sequence to achieve codeword framing. There is SYN. Following this is information transmitted in 64-bit code words based on a cyclic error detection/correction code, each code word containing 48 information bits and 16 error checking bits. Message's first code word AC
W contains address information and some data,
This first code word is sufficient to provide short messages such as status report messages and preliminary code messages. If the data message is long, additional code words DCIII, -DCW, are concatenated with the first code word Act■ as required for the service data.

The first retransmission protocol described in the aforementioned paper is called the simple retransmission protocol. In particular, in the second protocol, the transmitting device transmits the complete mesomessage and then waits for questions and answers (accrunocimento) from the receiving device. If this response is not received (5) or if retransmission is requested, the sending device retransmits the complete message and again attends the question and answer session. This message can be retransmitted up to a predetermined maximum number of times, and if the message is not answered, the transaction is terminated. The receiving device then decodes the synchronization word SYN (before being able to decode the data code word DCW for each transmission) and decodes the code word ACt! It is necessary to address I. Data words that can be decoded can be stored, and data words that cannot be decoded are ignored. The receiving device retrieves the data words from the retransmitted message, completes the message as necessary, and
Transmit an end-of-transaction response only if a complete message has been assembled (or receive a repeat of the message if the message was previously completed; the reason is that the previous response was not decoded or was delayed) ). This simple retransmission protocol can result in low throughput since each retransmission contains a complete message. Furthermore, this protocol is not suitable for group calls where the receiving device does not send a single question and answer message.

A second known retransmission protocol, referred to as a selective retransmission protocol, can increase throughput by not retransmitting data code words that have already been successfully decoded. In this second protocol, for each transmission received by the receiving device, the receiving device transmits a question and answer signal to identify which data words need to be retransmitted, thereby improving throughput. If a response word is not successfully received, the transmitting device repeats the previous transmission signal. The transaction is terminated when the receiving device receives a response signal indicating that it has assembled a complete message, or when the transmitting device has made a predetermined maximum number of transmissions. This second protocol also relies on response signals sent by the receiving device and is therefore not suitable for group calls.

Additional problems that arise with transmission protocols are ``duplicity'' of messages at the receiving device when retransmissions occur, ``dropping'' of messages at the receiving device due to disturbances during transmission, and e.g. ``lost'' messages due to the sender interpreting the response signal as being for the wrong message. ) is resolved. However, the communication protocol suffers from signaling overhead for call completion or call initiation. Therefore, these protocols are also not optimal for group calls.

While efficiency can be improved by transmitting data as a sequence of segments, it is known that such protocols require a call fulfillment step, which is an undesirable overhead, especially for small amounts of data. ing.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned drawbacks in data communication and to provide an even more efficient and flexible data communication method.

In accordance with the present invention, a method of data communication is provided in which each message has one or more segments and a message and segment identification is assigned to this or these segments.

In the case of a short message, eg less than 30 source data code words, this message is processed as one segment.

When carrying out the method according to the invention, it is necessary to introduce these respective segment identifications into all the transmitted segments and to introduce the message identification into at least the first segment of a long message or the only segment of a short message. Introduce applications.

In order to eliminate the possibility that retransmissions of the same segment will be treated as new messages, the receiving device should be provided with a resettable timer that, when started by the reception of a segment, can be used for a fixed duration or for a duration that can be dynamically determined relative to the length of the message: if during this duration another segment with the same segment identification is received and there is also a message identification. In this case, the receiving device treats this as a retransmission of the previous segment. However, if the above-mentioned segment is received after the expiration of the above-mentioned duration, this segment is treated as a new segment. It can be configured to be reset when the

If desired, data code words can be transmitted with arbitrary bit interleaving and complementary dynleaping upon reception. The decision to bit-interleave or not to bit-interleave a data code word can be made dynamically and can be made dependent on several factors, such as the capabilities of the decoder at the receiving device and the prevailing channel conditions. With bit interleaving, when burst errors occur during transmission, these errors disappear over several code words, thus allowing the code to compensate for the errors [with the benefit of increased raw power]. .

Therefore, the number of segments that need to be retransmitted is reduced. Under certain circumstances: Well, there are cases where bit interleaving is not desirable, so it is better to make bit interleaving optional. If the data code word is bit interleaved, an indicator, such as a flag, is introduced in the message to indicate to the receiving device that the data code word is being incrementally interleaved. The degree of increment may be made dependent on the length of one segment. The reason is that the number of code words in a segment can be changed. Also, regardless of the number of code words in one segment, all of these code words can be incremented. By making the degree of incrementing variable depending on the length of the segment, the benefits of bit interleaving can be maximized.

Message data can be encrypted, in which case
An indicator, e.g. a flag, may be introduced into the message to indicate to the receiving device that the message data has been encrypted.
Do as instructed. The need for encryption may depend on the characteristics of the message data itself and/or the selected address to which it is being sent. Both bit interleaving and encryption can be used together.

The efficiency of the data message protocol can be increased by segments having data code words to be retransmitted together with new code words concatenated with data code words to be retransmitted.

The invention will now be explained with reference to FIGS. 2 to 5.

In the message data transmission method according to the invention, the concatenated data code words are arranged into a number of segments and each segment is sent sequentially.

Message and segment identification means, such as sequence numbers, are used to recognize duplicate messages at the receiving device. Message data is sent in segments, thereby aborting the transaction early if the channel is insufficient for transmission, and sending the first portion of the message to its destination before the entire transaction is completed. Furthermore, segment 1H also improves throughput and reduces delay by reducing the amount of repetition.

When formatting a message, each segment includes a preamble, a synchronization string, an address code word followed by a plurality (typically 1 to 3) of data code words DCi'l. .

Message and segment identification numbers are placed in each segment, for example in the first data code word following the address code word.

64 pid r address code word 8C of one segment
The format of W is shown in FIG. 2, and the format of the first data code word D CW 1 is shown in FIG.

Address code word and first data code word DCW
Also shown is the number of bits used in each part of I.

The address code word AC in FIG. Q ”) is used to indicate
,) is being done. PFIX is a prefix address. IDENTI is the address of a receiving device or a group of receiving devices. The C1 entry indicates that this address code word is of the category used for message data forwarding. 5EGL represents the number of data code words concatenated following the address code word. In this case, 5 bits are allocated, so the maximum number is 31 unless these digits are signed 1. I
DENT2 is the address of the transmitting device. CRY
PT has the residue "O" if the data code word is not encrypted and has the value "1" if the data code word is encrypted. The last field (last part) P has parity check bits for error correction or error detection. Parts EXT and FLA not mentioned above
GI and FLAG2 are not important as far as the understanding of the invention is concerned.

In FIG. 3, the first data code word D Cl'+
The first bit of 1 is '0' indicating that this word is a data code word.5PEC can be used, for example, to represent a particular type or structure of data, or to assign data to a particular peripheral address. It can be used for.

N5EG indicates the segment number.

N II +, (indicates the number of times the code word is repeated in the message number or segment. In particular, N5EG
=0 to indicate the first segment of the message, then NUM=NMESS, and if NS[EG is not equal to O, then N[, I M = NRE P. where N', lESS is the message number and NREP is the number of code words repeated in the segment and is set to zero for non-selective transmission. L.A.
ST is all zero except for the last segment of the message. The last code word of segment LAST indicates the number of data bits used in the code word.

When C=1, CRC f, yield is [CITT
A 16-bit checksum is included in accordance with the recommendations of the International Telegraph and Telephone Advisory Committee (International Telegraph and Telephone Advisory Committee). Alternatively, if C has the value "o", the data is not protected by a checksum placed in the CRC field;
In this case, the second field is customization (
custom-misation).

R3VO is a dedicated bit and the last one
The 6-bit P is a parity check bit for the 64-bit code.

When forming segments, the data code words may be constructed by selective bit interleaving. In this bit interleaving, data code words are read into two-dimensional storage in a row-sequential direction and read out in a column-sequential direction, so that all first bits are read, then all second bits are read. , and so on are sequentially read out in the same manner.

This means that if there are burst errors during transmission, these errors will be distributed over the data code word, reducing the possibility of errors occurring in the receiving device beyond the error correction capacity of the decoder. means. Therefore, the amount of retransmission can be reduced. The use of optional bit interleaving pins depends on the length at which burst errors can occur, the number of data code words in the segment to be incremented, and the error correction mode at the receiver. Furthermore, the receiving device needs to be capable of dinterleaping the incrementally-creeped data.

If desired, the data code word can be encrypted, in which case an indication bit, eg a flag, is inserted into the message to indicate to the receiving device that the message data is encrypted. The data code words are optionally bit interleaved before being encrypted.

FIG. 4 shows the response address code word ACKO for a data segment sent by a receiving device to a transmitting device. The first bit has the value "1" indicating that this code word is an address code word. PFiX is a prefoot address and ID
ENTI is the address of the receiving device responding to the data segment. CAT indicates that this address code word is of the category used in the response, and TYPE indicates, for example, whether the segment was successfully decoded or whether the segment is selective (transmission or non-selective retransmission). IDENT2 indicates the identification of the device that sent the data segment.NEW has the value ``0'' when a non-zero segment number is responded. , has the value "1" if a segment number of zero (i.e., the first segment of a new message) is being responded to. A N U !
J is the response number, NEIV
=O(D, then ANUM= (N5E preceded by zero
G) With Te, NEW = 1 (7) Case i: C, in each case (if segment is answered) A N
U M = N 14 E SS. P is an odd-even check (parity check) for a 64-bit code word
Indicates a bit.

In the case of a response address code word requesting selective retransmission, a control data word as shown in FIG. 5 follows. The main field is 5IELF with a selective retransmission flag indicating which source (atomic) data code word of the segment requires retransmission. One bit is assigned to each data code word, where "o" indicates no repetition is requested and "l" indicates that the associated data code word is requested to be repeated. . The most significant bit in the 5IELF field corresponds to the first transmitted source data code word in the segment. If the segment contains fewer than 30 source data code words, retransmission information is placed in the most significant bits of the SεLF field.

Subsequent unused bits are set to zero.

Next, the steps of the protocol will be described for a call to a single recipient.

In operation, the sender encodes the source data in the order of data code words. Forty-seven data bits are used in each data code word. If necessary, zeros are added following the source data to terminate the final data code word. Messages occupying fewer than 30 source data code words can be sent as one segment. Messages longer than that must be broken up and sent as multiple segments. Each segment can have up to 30 source data code words.

A heading is placed at the beginning of each segment. The headings are preamble inversion, code word synchronization sequence SYN,
Address code word A CW and control data code word DCI! It has. The fields in ACIQ and DCWI are set appropriately. Message number N M E S S is the destination (location where data is transmitted)
increases modulo -128 for each new message transmitted regardless of the Segment number N5EG is set to zero at the beginning of each new message and increases modulo -64 for each new segment transmitted.

N5EG is not increased for the same repeated transmission.

Optionally, a CRC can be calculated and included in the control data code word. Again, the data code word can be encrypted and bit interleaved, or only one of these can be performed. The sender only needs to perform incrementing by prior arrangement with the recipient. The sender transmits the segment and waits for a response from the receiver. The TYPE field in the response represents the meaning of the response. For example, it indicates whether a segment was successfully decoded (ACKDD) or whether selective retransmission (8 CKDS) or non-selective retransmission (ACKDR) was requested.

After receiving the response, the sender may retransmit the same segment, perform a selective retransmission, transmit the next segment, consider the call successfully completed, or abort the transaction.

If no response is received, the sender may retransmit the segment.

The sender can repeat the same segment up to a predetermined number of times per segment and wait for a response after each transmission.

If selective retransmission is required but the sender is unable to perform selective retransmission, the sender may similarly retransmit the previous segment.

If you are sending selectable 1, select segment number N.
5EG is increased. Repeated source data code words are first transmitted in a segment and then new source data code words can be placed into this segment for a total of 30 source data code words.

Control data code word [lC (in S1, NUM=N
REP (number of repeated source data code words)
becomes.

Thus, time can be saved by not devoting an entire segment to retransmissions of selected codewords that include transmissions of other header or address codewords.

On the receiving device side, message and segment numbers are used to ensure that segments are not duplicated or to allow the receiving device to identify when omissions have occurred, and to ensure that segments from different messages are received as a single message. Make sure not to.

A timer in the receiving device is started each time a segment is received. The timer runs for a period related to the length of the segment. The first receiver memorizes the value of N5EG and the value of N'JESS that was received the latest. (x!, 1ES
S appears at least in the first segment of each message).

While the timer is running, the receiver receives N1. N ESS received before! , IESS, the segment with N5EG=0 can be received as the start of a new message, otherwise it can be received as a repetition of the first segment of the previous message.

Also, while the timer is running, the receiver can receive a segment in the ongoing message sequence only if one shift of N5EG increases by l (modulo 64) from the value of N5EG of the previously received segment. .

Also, while the timer is running, the receiver can receive the segment as a repeated transmission of consecutive segments only if the segment number (NSEG>) is the same as the number of the previously received segment.

The last segment of the message is not L A S T
5).

Once the receiving device has decoded the A Civ and DCiGl of an acceptable segment, i.e. a segment that satisfies the aforementioned conditions and an acceptable IDENTI, it decodes the number of the next data code word represented by 5EGI. . At this time, if CRYPT = 1, first; this code word is decrypted, and if INT = 1, the next code word is dinterleaped.

The recipient may request to be able to decode all of the data code words before responding with ACKDD.

Alternatively, if the control data code words are successfully decoded, only the decodable source data code words can be stored and the rest assembled using repeated transmissions.

The receiving device sends a response for each acceptable segment. Also, non-selective retransmission is requested by ACKDH. Selective retransmission is requested by ACKDS.

In the case of a group call, the receiver does not transmit a response. In the case of group calls, segment sequential message transmission can be accomplished by retransmitting each segment up to a predetermined number of times before proceeding with the next segment. In any case, number the messages and segments.

When determining the duration of the timer period, this duration must be related to the duration for a given number of transmissions of one segment. This decision takes into account the length of the segment, eg the total length of the address code word and 31 data code words, and the maximum number of times the segment may be transmitted, eg 8 times.

Message numbering is determined by considering the maximum number of messages that can be sent during the maximum timer duration, so if we send 128 (short) messages during the timer duration, then The numbering order of messages before being repeated again must be at least 0-127. If there are too few numbers, no new messages can be sent for the remainder of the timer duration when all message numbers are used.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a typical data format. FIG. 2 is an explanatory diagram showing the format of an address code word expression C1 that forms part of the segment heading. 1 data code word DCII
4 shows the format of the response address code word ACKO sent by the receiving device. FIG. 5 shows the format of the optional data code word following the response address code word. FIG. PR...Preamble SYN...Synchronization column AC1'l...Address code word DCI...Data code word PFIX...Prefix address IDENTI...
...Address IOεNT of a receiving device or a group of receiving devices
2...Address of transmitting device INT...Increasing CRYPT...Cryptography (Hi) N5EG/Segment number NIJM...Message number or code word repetition count 8ST...Last segment P...Odd-even Check bit ACKO...Response address code word Patent applicant
N.B. Philips Fluiran Pen Fabricen

Claims (1)

Claims: 1. A data communication method in which each message has one or more segments, characterized in that a message and segment identification are assigned to this or these segments. 2. In the data communication method as claimed in claim 1, a short segment is treated as a single segment with its own message and segment identification, and both of these messages and segment identification are A data communication method characterized by transmitting. 3. In the data communication method as set forth in claim 1, a long data message is divided into a plurality of segments, each segment is assigned its message and segment identification, and at least the first A data communication method characterized in that the segment includes message identification at the time of transmission. 4. The data communication method according to any one of claims 1 to 3, wherein the reception of a segment to which the same identification as a previously received segment is assigned within a predetermined period is A data communication method characterized in that segments received before are processed as repeated transmissions. 5. In the data communication method according to any one of claims 1 to 3, within a dynamically determined period of a segment to which the same identification as a previously received segment is assigned. A data communication method, characterized in that reception of the previously received segment is processed as repeated transmission of the previously received segment. 6. In the data communication method according to claim 4 or 5, the reception of a message to which the same identification as the previous message is assigned after the end of the period is defined as a new message. A data communication method characterized by processing as follows. 7. The data communication method according to any one of claims 4 to 6, characterized in that the duration of the period is related to the maximum number of times the segment can be transmitted and the length of the segment. data communication method. 8. A data communication method according to any one of claims 1 to 7, characterized in that a response signal is sent after receiving the segment. 9. In the data communication method according to claim 8, a plurality of types of responses each representing whether a segment has been successfully decoded or whether retransmission of part or all of a segment is required. A data communication method characterized by introducing a signal. 10. A data communication method according to claim 9, characterized in that one segment comprises a retransmitted data code word and a new data code word. 11. A data communication method according to any one of claims 1 to 10, in which each segment comprises a heading having an address code word and a first data code word containing a message and segment identification. A data communication method characterized by having the following. 12. The data communication method according to any one of claims 1 to 11, characterized in that message data is bit-interleaved and this message data is sent together with an instruction representing this. Communication method. 13. The data communication method according to claim 12, wherein the degree of bit interleaving is made dependent on the length of the segment. 14. In the data communication method according to any one of claims 1 to 13, the message data is encrypted and the message data is sent together with an instruction indicating that the data is encrypted. A data communication method characterized by transmitting data.